1. Field of the Invention
The present invention relates to an image-recording material, an image-recording process and an apparatus therefor. More particularly, it relates to an image-recording material enabling visible images with a high optical density to be formed by energizing an image-recording layer containing a trivalent cobalt complex compound to form a latent image or a primitive visible image in the image-recording layer and developing the image-recording layer in a dry process; an image-recording process; and an apparatus therefor.
2. Description of the Prior Art
Of image-recording processes, particularly well known and excellent processes can be classified in a broad sense as photography, thermography, electrophotography, and combinations of two or more of these arts such as heat-sensitive photography. Additionally, the terms of photography, thermography and electrophotography as used in this specification mean image-recording processes. In these processes, light, heat and electrical phenomena are utilized, respectively, for recording and reproducing a pattern in a visible form. These known image-recording processes possess intrinsic advantages in particular uses but, in other uses, they have various defects limiting their utility. For example, conventional photography using a silver halide emulsion has the defect that a wet and chemical developing step is required, thermography requires heating a latent image, and one embodiment of electrophotography, xerography, requires a mechanical transfer of a powder pattern.
It is well known to form images in a recording layer of a specific recording material by passing a current in the interior of the recording layer thereof. For example, K. S. Lion et al. in "Investigation in the Field of Image Intensification, Final Report", Air Force Cambridge Research Laboratory (AFCRL), 64-138, Jan. 31, 1964, Contract No. AF 19(605) -- 5704 discloses such a photographic process. In this recording material, an ordinary light-sensitive photographic emulsion layer is provided adjacent a photoconductive layer. A uniform electric field is applied across the photoconductive layer and the photographic layer and, at the same time, the photoconductive layer is imagewise exposed with a light pattern, followed by passing a current through the photographic layer in an image-wise manner.
The recording process of Lion et al, supra, has the advantage of an increase in sensitivity, but it has the defects resulting from the use of a light-sensitive layer which must be chemically developed. Further, since a latent image is formed in the conventional light-sensitive photographic emulsion, it is necessary to generate a substantial current flow in the photographic emulsion. Therefore, where the current is low, a comparatively long exposure time is necessary or, where the exposure time is short, a large current is necessary.
Another process for forming visible images is disclosed in U.S. Pat. No. 3,138,547. This process includes the use of a light-insensitive, electron-sensitive recording layer of reducible metal compound particles capable of being electrically reduced in development (in situ). This recording layer is provided on a support with an electrically conductive layer thereon, and recording is effected by contacting the layer with an electrically charged needle to generate a current flow in the recording layer. In this case, sufficient current to form a visible image by reducing a specific metal compound in a dry state is passed.
The defect of the above-described recording process disclosed in U.S. Pat. No. 3,138,547 is that image gain or amplification is not possible.
A further process is disclosed in U.S. Pat. Nos. 2,798,959 and 2,798,960. According to the disclosure of these patents, a photoconductive material and a heat-sensitive material are sandwiched between a pair of electrodes and, at the same time, they are brought into electric contact with these electrodes. An electric potential is applied across these electrodes, during which time an optical image is projected on the photoconductive material. By passing a current, the photoconductive material is heated according to the current. The heated image thus formed in the photoconductive material subsequently changes the heat-sensitive material to form a permanent image there.
One defect of this recording process of U.S. Pat. Nos. 2,798,959 and 2,798,960 is that it is necessary to pass a large current in the photoconductive material in order to supply enough heat energy to form an image. Further, just as is the case with the process of U.S. Pat. No. 3,138,547, in order to attain an increase in the density of the final image, the current must be increased.
An image-recording process including image amplification (or image intensification) is disclosed in U.S. Pat. No. 3,425,916. According to this process, a reagent layer is imagewise exposed to a comparatively small current to form chemically developable nuclei in the reagent layer. Then, the layer is subjected to chemical development for amplification, thus forming a visible image.
The process of U.S. Pat. No. 3,425,916 requires only a comparatively small current for forming a developable latent image. However, this process requires that a recording material to be used therefor be moistened during the latent image-forming step or nuclei-forming step. In addition, visible images formed through development must immediately be stabilized through washing and fixing just as in an ordinary photographic process. This process has not so far been commercially utilized for the above-described and other reasons.